2 Tek Modlu Fiberde (SMF) İletim BandlarıSMF zayıflama eğrisi700130011009001700 nm1500GörülebilirKızılötesi“L” Bandı ~ nm“O” Bandı ~ nm“C” Bandı ~ nm“S” Bandı ~ nm“E” Bandı ~ nmFirst of all, I would like to mention about present transmission bands and attenuation spectrum in single mode fiber. The wavelength region of single mode fiber with the lowest attenuation is called third window or 1.55 µm window. Because of low attenuation, erbium doped fiber amplifiers have been initially developed for optical signal amplification in the conventional band (C band, nm). And now, they are under investigation to cover the long wavelength band (L-band, nm) with an inherent flat gain spectrum. A combined C and L bands will offer a much wider transmission window for the dense WDM systems.Şekil 1. Işık SpektrumuAhmet Altuncu, Arif Başgümüş, Dumlupınar Üniversitesi

5 Simülasyon Sonuçları (a) Kazanç SpektrumuIn the simulations, the total bidirectionally applied pump power was 2x150 mW and the signal input power was dBm for each channel assuming 100 WDM channels in total from 1520 nm to 1635 nm.Figures 4a and b show the gain and noise figure spectra of bidirectionally pumped EDFA with different fiber lengths varying from 5 m to 100 m. For short fiber lengths (5-10 m), the EDFA operates completely in C band. When the EDF length increases to longer than 30 m, the gain spectrum of the EDFA shifts to longer wavelength band (L band) and gives almost no gain in C band. The gain spectrum shift is nearly proportional to EDF length although the net gain decreases for longer lengths than 75 m due to insufficient pumping conditions.For short fiber lengths (5-10 m), the noise figure of the EDFA is as low as 4 dB due to high gain of the C band EDFA. On the other hand, the low noise region of the amplifier also shifts to longer wavelength region for longer lengths and the noise figure is higher with respect to C band.(a) Kazanç Spektrumu(b) Gürültü Faktörü SpektrumuŞekil nm’de çift yönlü pompalanan bir EDFA’da kazanç ve gürültü faktörü spektrumlarınınfiber uzunluğu ile değişimi.(Pp = 2x 150 mW, Psig = -30 dBm, nm arasında 100 WDM kanal varsayılmaktadır.)Ahmet Altuncu, Arif Başgümüş, Dumlupınar Üniversitesi

11 L Bandı Döngü Tipi EDFA Deneysel Sonuçları-3Fig.15 shows the measured gain and noise figure spectra of L-EDFA between nm. The spectral gain and NF measurements were limited to 1585 nm at L band due to unavailability of the TLS operation beyond this wavelength. It can be seen on the figure that the L-EDFA gain increases with increasing wavelength up to 1585 nm. Although the gain and NF performance of L-EDFA at nm is worse, they become moderate at 1585 nm as 18.3 dB and 7.1 dB, respectively.From the output ASE spectrum of L-EDFA observed on OSA, the L-EDFA design is estimated to provide an approximately 40 nm gain bandwidth between nm for saturating signal powers.Şekil 8. Klasik ve döngü tipi L-EDFA konfigürasyonları için kazanç ve gürültü faktörünün giriş sinyal gücü ile değişimi. (sig = 1585 nm, Pp.tot = mW)Ahmet Altuncu, Arif Başgümüş, Dumlupınar Üniversitesi